Assembling fittings, connectors or couplings and the like with a tube can be difficult in some aspects. For example, if the tube is flexible it may tend to bend or twist under the force required to seat the tube onto a fitting and if the tube is relatively stiff, it may break if not appropriately held and/or aligned with the fitting during assembly. Present approaches to assembling a fitting into the end of a tube suffer from a variety of drawbacks, limitations, disadvantages and problems including the length of time and potential for damage to the tube and/or fitting during the assembly process. There is a need for the unique and inventive assembly tool and method for installing fittings and tubes to one another.